A fluororubber is excellent in heat resistance, chemical resistance, oil resistance, weather resistance, etc. and is used for application in a severe environment in which a general purpose rubber cannot be used.
As a known fluororubber, a vinylidene fluoride/hexafluoropropylene copolymer, a tetrafluoroethylene/propylene copolymer or a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer may, for example, be mentioned. Among them, a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer is also called a perfluoroelastomer and is excellent in heat resistance and chemical resistance.
As a known perfluoroelastomer, for example, Patent Document 1 discloses a copolymer of tetrafluoroethylene (hereinafter referred to as “TFE”) and perfluoro(methyl vinyl ether) (hereinafter referred to as “PMVE”).
Further, Patent Document 2 discloses a copolymer of TFE, PMVE and perfluoro(propyl vinyl ether) (hereinafter referred to as “PPVE”).